This invention relates to a coil of, for example, an electric implement coated with electrically insulating plastics material and a method of applying said electrically insulating plastics material.
The conventional process of electrically insulating an electric implement coil generally comprises winding the coil with, for example, an electrically insulating material to provide an electric insulation layer, impregnating said electric insulation layer with thermosetting resin in vacuum, and later thermally hardening said resin.
The object of impregnating thermosetting resin in an electric insulation layer formed of, for example, an electrically insulating tape is intended to meet the undermentioned requirements.
(1) For example, moisture or dust tends to be carried into an electric insulation layer if formed of only an electrically insulating tape. Therefore, it is desired to prevent the intrusion of such undesirable foreign matter in order to more effectively save an electric implement from moisture and contamination.
(2) It is necessary to eliminate the presence of void spaces in the electric insulation layer, thereby suppressing the occurrence of an electrically harmful corona.
(3) The heat conductivity of an electric implement should be elevated, to reduce the rate of temperature rise in the electric implement.
To thoroughly attain the above-listed objects, it is important that thermosetting resin be sufficiently impregnated in the electric insulation layer to eliminate the presence of any void space in said electric insulation layer.
However, the conventional process of effecting the above-mentioned electric insulation is accompanied with the drawbacks that while thermosetting resin impregnated in an electric insulation layer formed of, for example, an electrically insulating tape, is being hardened, said resin is temporarily reduced in viscosity by application of heat; and part of the impregnated resin flows out of the electric insulation layer, resulting in the occurrence of void space in said electric insulation layer, presenting considerable difficulties in fully attaining the aforementioned objects.
The conventional process of electric insulation has the drawbacks that a hardening agent, catalyst, monomer, etc. tend to scatter during a period in which a thermosetting resin is fully hardened, exerting harmful effects from the standpoint of meeting safety and sanitary requirements and preventing environmental pollution.